As the others have said, it's all in the variables. What level of resort (and on-site, off-site, dvc rental), how many days (3, 4, 14?), what kind of dining (plan, no plan, mostly QS, all QS, all TS, all Signature), what time of year (super low, moderate, super busy)? All of these will play big roles in your total cost.
As an example, my trips have been running me ~$2500-$2800. These are 10 day trips at a moderate resort in September with Deluxe Dining and park hopping utilizing either Free Dining (this year) or 30% room discount (2010, 2011). I could easily get away cheaper or I could just as easily spend twice as much*.
As an illustration of the range and how dependent it is, let's throw some numbers...
Two trips, both 7 nights (Wed - Wed, it's cheaper to fly during the week). One in mid-Sept, one over Christmas.
ASMu - September, 8 day base tix and room = ~$1,000
ASMu - Christmas, 8 day base tix and room = $1,500
Poly - September, 8 day hopper tix, room, Deluxe Dining = ~$4,200
Poly - Christmas, 8 day hopper tix, room, Deluxe Dining = ~$5,600
Note that neither of these packages have any discounts applied, which are relatively common in the low seasons (so, September in this example), so those prices may drop a bit. Note also that there is a lot of middle ground between value with base tickets and no food plan and deluxe with hoppers and deluxe dining. Without knowing what you're looking to experience though, it'd be tough to give an estimate with any accuracy at all.
What I would do in your shoes, is price up the packages for next year when they come out (rumored to be on July 11) for approximately the time you'd want to visit and see what you can come up with. Figure ~10-15% increase per year just to get a closer estimate (none of this is exact, and it's better to overestimate and underspend, than the reverse

)
*By easily spend twice as much... I mean I could come up with a trip that costs twice as much. I'd not be able to pay for it though
